Monday, November 8, 2010

Sling Index

The Sling Index calculates slinging accuracy as margin of error in the angle of each shot.  Assuming a circular target area.  The point of release, the center of the target, and the edge of the target form a right-triangle.  At the vertex where the slinger stands the angle gets smaller and smaller as the accuracy of the slinger improves since both increased distance and decreased target area shrink the angle.  Therefore the lower the Sling Index, the smaller the angle of error possible to still allow a hit on the target, and therefore the better the accuracy.

I was asked recently how accurate I was at slinging and found the question difficult to answer.  The size of the target, how many shots I took at it, and of course the all important, how far away I was, all depend on the likely hood of me hitting the target.  I've slung with high and low percentages but the situations were  not comparable.  There must be a way to level the playing field, so that no matter what I'm slinging at and how far away I am, I can have a gauge for the level of accuracy I'm attaining to.  To accomplish this from now on I'll be using the Sling Index.

Sling Index equals the inverse tangent of the target radius dividing by the distance of the target.  So if the radius of your target is the same as your distance from the target, the sling index is 45.  A very easy shot. At ten feet your target would be 300 square feet, about the size of a house.  Conversely, if you are 19 feet from a 3 square foot target, the sling index is just over 3.  A difficult shot, like standing on the sidelines of a football field and hitting a beach ball half way between you and the center of the field.  This graph gives some idea as to how quickly the Sling Index drops with  distance from a 1 square unit target.

9 comments:

  1. The units appear a little unclear. The sling index is really just half the max. angle of spreadthat your shots can have. This is an easy calculation if you know the dimension rather than the area. Your example of a 3 square foot circular target will give a radius of a whisker under 1' or a diameter of 2'. I think it more likely that someone will know the size of his target rather than its area.

    Aussie

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  2. I'm not sure what my sling index would be, but at my best I could consistently place my shots within a 3' circle from 35' away. (Damn, now I want to go out and practice my accuracy... Even though I should be job-hunting...)

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  3. The thing that led me away from archery to slinging was the instinctive nature of it,shooting whether it be a bow or a rifle requires stillness and careful aim,slinging requires fast fluid motion and the aiming is done on the fly,and when it happens and you make that perfect shot without thinking about it,its a Zen moment,a true fusion of mind,body and weapon,what Musashi called "mind/no mind".
    I think its a mistake to try and quantify it with mathematics,Slinging is far more than mere physics.

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  4. Aussie, yeah... you're right... the numbers are wonky because they're kind of too difficult. I just wanted a quick way to get a feel for how I was progressing... but suppose that this could more easily accomplished with a home built target and measured distances with 5 throws each. Even once a month at this would be good enough, I just hardly ever sling in the same place.

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  5. Anonymous... maybe you could make slings and compete with me. :) Good luck it's a tiny market. Or better yet, maybe you could make your own woven slings and sell them on my site... just an idea... but that's not a real job is it...? It'd be weekend doughnut money...maybe. hope you find one.

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  6. Andy, you could not be more right. Just after I wrote this I abandoned it. Partially because it's too difficult to do on the fly and often my target can't be measured because I can't even get close to it, or don't have time. In the end I just like slinging. I don't really care how much better I am. I just enjoy trying it's actually the difficulty that draws me... and I loved your description... the fluid on the fly, I always thought of it as feeling the sling. You can't get better at slinging by reading a book, you just have to go out and chuck a lot of rocks... thanks for the comment... what length sling do you use?

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  7. Glen;I use slings of about 22",I`m a short guy and a longer sling feels kinda unwieldy,besides I`m more into short range accuracy than going for distance.

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  8. 22"? Quite short, it is true that the longer slings are more difficult to handle, and much worse at accuracy. I've even found that I'm not very good at slinging short slings because it's a completely different style. The dynamics change. Can you send me a picture of your sling?

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  9. I cant send you a pic but you can see the type of sling i use if you go to "bushcraft on fire" on youtube.Made from a single piece of cord,not terribly authentic from a historical POV but I was always more interested in the purely martial aspects rather than the historic ones.
    I generally train in 2 throwing styles,figure 8 and Greek,seems to me that figure 8 is better for troops in the field in formation while Greek is better for throwing from behind cover,and my criteria is simple,can I hit a man from 50 yards away?

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